|Publication number||US4846404 A|
|Application number||US 07/150,138|
|Publication date||Jul 11, 1989|
|Filing date||Jan 29, 1988|
|Priority date||Jan 29, 1988|
|Also published as||CA1323932C|
|Publication number||07150138, 150138, US 4846404 A, US 4846404A, US-A-4846404, US4846404 A, US4846404A|
|Inventors||James E. Smith|
|Original Assignee||Graves Spray Supply, Inc.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (9), Classifications (14), Legal Events (4)|
|External Links: USPTO, USPTO Assignment, Espacenet|
The present invention relates generally to two component mixers and sprayers and more specifically to an internal mixer and sprayer capable of being used with any two component systems and specifically for polyester foams and resins.
Fiberglass spraying devices, and particularly hand held units, have previously employed a number of different spraying methods in attempts to provide well-mixed, properly shaped fluid spray flows in the most efficient manner possible. Typical fiberglass spraying apparatus supply fluid resin and fluid catalyst to a nozzle for internal or external mixing. With internal mixing, catalyst fluid may typically first be atomized by mixing with air and then directed into the path of the fluid resin at the nozzle interior. After resin-catalyst mixing, the resulting fluid is forced through a common nozzle and directed at the work piece. Internal mixing requires time consuming and expensive cleaning of the nozzle and mix chambers after each use.
With external mixing, both catalyst and resin fluids may typically be forced though separate spray nozzles prior to mixing. These nozzles are directed such that the catalyst and resin spray flows intersect to permit mixing prior to contact with the work piece. If the resin is not atomized prior to spraying, the process is often called "airless." Such external mixed sprayers may not need extensive cleaning after each use, but typically require high fluid pressures. Reinforcing fibers may typically be directed into the mixed spray path of either internal or external mix sprayers to be wetted thereby and carried to the work piece.
The difference between paint spraying and resin spraying has been recognized by many including the state of California which enacted a new rule 1162 directed to polyester resin operations. This rule defines what comes under the statute as well as the special health compliances. Polyester resin spray facilities must be in compliance by July 1, 1988.
For emission control as well as waste purposes, it is desirable to use an internal mix which uses the minimum amount of catalyst or resin. A polyester foam which cures faster and is safer environmentally has been developed by Alpha Corporation. The Alcel polyester foam has a high viscosity in the range of 3600 centipoise compared to 300 centipoise for normal sprayable resins. To produce a foam in the range of 25 to 30 pounds per cubic foot, 3% of blowing agent and 2% of catalysts are added to the Alcel polyester resin. Alcel also offers a filled resin with 40% filler and 60% foam having a viscosity in the range of 120 centipoise. The suggested use is 1.75% of blowing agent and 1.25% catalyst by compound weight. This produces a density in the range of 40 to 50 pounds per cubic foot.
In order to internally mix polyester foams and resins the prior art has used high pressure to force the catalyst and blowing agent into the resin and thus, required substantially long restrictors and surge tanks. The resin and catalyst are introduced at high pressures in opposite directions towards each other to begin the mixing. Similarly, they required static mixers to assure mixing of the catalyst and blowing agent with the resin. Additionally, the catalyst has been provided at four to seven times the pressure of the resin to assure mixing. When the nozzle size or primary material pressures were changed, the system had to be totally rebalanced. Examples of these types of spray guns and systems are shown in U.S. Pats. Nos. 3,709,468 and 3,790,030.
Thus, it is an object of the present invention to provide an improved airless, internal mix sprayer for mixing a small amount of catalyst or secondary fluid to a large amount of primary fluid wherein the mixing balance is self adjusting.
Another object of the present invention is to provide an internal mixer which is capable of operating at reduced supply pressures.
Another object of the present invention is to provide an internal mixer without static mixers.
A still further object of the present invention is to provide an internal mixer for primary and secondary fluids without the need for substantial restriction and surge tanks in the secondary supply lines.
A still even further object of the present invention is to provide an internal mixer which is self-balancing for the changing of spraying nozzle sizes and pressures.
A still even further object of the present invention is to provide a cartridge which is mounted to the face of an existing gun to provide internal mixing of fluids.
These and other objects of the present invention are achieved by introducing a secondary fluid or catalyst radially into a first axial bore and introducing a primary fluid or resin axially to flow through the secondary fluid to be mixed therewith. Preferably the secondary fluid is introduced radially with a circumferential rotation and the primary fluid is introduced as an axial annulus. This allows the system to be self-balancing and the secondary fluid to be introduced at a relative low pressure. The secondary fluid is introduced through a circumferential orifice which is sufficiently small such that there is a pressure change produced by the flowing primary fluid such that the ratio of inlet pressure of the secondary fluid to primary fluid remains substantially constant for variations of flow rates. A substantially short annular restrictor is used in the secondary fluid inlet to prevent surges and act as an accumulator.
The primary fluid is introduced through the interior of a reducing element and then radially to its exterior to form an axial annulus. The reducing element extends from an axial position at which the primary fluid is introduced radially past the axial position at which the secondary fluid is introduced to form a first annular passage. A dispersing chamber is provided axial between the reducing element and the spray nozzle of a substantially larger cross-sectional area than the cross-sectional area of the primary annulus to further mix the primary and secondary fluids by turbulence produced by the change of cross-sectional area.
The secondary fluid from the secondary fluid inlet is introduced tangentially to a second annular passage connected to the circumferential orifice to produce the circumferential rotation of the secondary fluid at the circumferential orifice. The cross-sectional area of the second annular passage is larger at the point of introduction from the inlet than the cross-sectional area where it is connected to the circumferential orifice. The width of the circumferential orifice is smaller than the cross-sectional area of the second annular passage.
An air nozzle is provided adjacent to the spray nozzle for producing an axial flow for maintaining a substantially homogeneous mixture of primary and secondary fluids and/or further shaping of the spray pattern. The primary fluid may be a polyester resin or a foaming polyester resin which is premixed in a mixing chamber before being introduced to the first annular passage where it is mixed with a secondary fluid or catalyst.
The internal mix is formed as a cartridge which can be part of a spray gun or a separate cartridge that can be added to reexisting guns to convert an external mixture to an internal mixer.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.
FIG. 1 is an exploded view of the portions of a spray gun including an internal mixing chamber incorporating the principles of the present invention.
FIG. 2 is a cross-sectional cut-away version of the internal mixing portion of the spray gun of FIG. 1.
FIG. 3 is a cross-sectional area taken along lines III--III of FIG. 2.
FIG. 4 shows an annular restrictor according to the principles of the present invention.
FIG. 1 shows a gun having a housing 10 with resin inlet 12, blowing agent inlet 14 and catalyst inlet 16, generally shown in the rear thereof. Additionally, for an air assist system, an air inlet 18 is provided and for cleaning, a cleaning or solvent inlet 20 is also shown. A mixed resin/catalyst nozzle 24 and an air assist nozzle portion 26 are secured to the housing 10 by a nut 28 which is threadedly received on the housing 10. The air assist nozzle portion 26 provides air to surround the mixed fluid stream to maintain the mixture confined to a spray pattern and maintain the mixture substantially homogeneous. The air also can perform further shaping. In either case, the air assist prevents the formation of tails or splitting of the spray pattern. The internal mixing cartridge 30 is provided between the housing 10 and the nozzle 22.
The internal mixing cartridge 30, which is illustrated in detail in FIGS. 2 and 3, includes a generally cylindrical housing member 32 having a bore defining element 34 inserted in a cylindrical recess 36. A first axial bore 38 is provided in the bore defining element 34 which will define the mixing chamber. A second axial bore 40 through bore defining element 34 is connected to the catalyst inlet 16 through the gun. A third axial bore 41, through the bore defining element 34 and housing member 32, connects the air inlet 18 and the air assist nozzle portion 26. In an orifice 42 in the front wall of the housing member 32 is a cylindrical insert 44 which defines an extension of the first bore 38 on its interior and, as will be described later, defines part of the passages of the catalyst on its exterior. The mixed resin/catalyst nozzle portion is received in the interior of insert 44.
As illustrated specifically in FIG. 3, the outer housing 32 has a recess 50 which defines a passage having an annular portion 48 about the exterior of the insert 44 and is connected to the second axial bore 40 connected to the catalyst inlet by a tangential section 50. The tangential entry and reduction of cross-sectional area between the second axial bore 40 and tangential entry 50 and the annular passage 48 produces an increased pressure, circumferential swirling motion to the catalyst. The bore defining element 34 has a recess 52 and 54 axially adjacent to the housing 32. The recess 52 defines with insert 44 an annular passage of the same cross-section as the annular portion 48 of the passage 46 in the housing 32. The recess 54 with the insert 44 defines an annular passage 53 having has a substantially smaller cross-sectional area than the annular element passages 52 and 48. The annular passage 53 is connected through a circumferential orifice 56 into the first axial bore 38. The circumferential orifice 56 is defined by the separation of the insert 44 from the bore defining element 34. The width of circumferential orifice 56 is smaller than the width or cross-sectional area of passage 53.
The flow of the catalyst from the second axial bore 40 through the tangential entry passage 50 and annular passages 48 andn 52 into a smaller diameter annular portion 53 to orifice 56 provides a radial sheet of catalyst having circumferential rotation. This rotation through the various passages equalizes the fluid pressure and flow across the cross-sectional areas of the reduced passage 53 and the circumferential recess 56. This assures that the catalyst being introduced into the first bore 38 is uniform throughout as well as substantially in balance. Similary, the annular rotation provides additional momentum and forces to assure a proper mixing of the catalyst with the primary fluid flowing in the first bore 38.
A reducing element 60 is provided in the first bore 38 and sealed thereto by an O-ring 62. The reducing element 60 provides an annular area 64 in the first bore 38. The reducing element 60 includes an internal bore 66 into which the primary fluid, being for example resin with a blowing agent mixed in the gun prior to the reducing element 60, is introduced into the annular section 64 of the bore 38 by a plurality of radial orifices 68. Reducing element 60 extends from the radial orifices 68 at which the primary fluid is introduced past the circumferential orifice 56 at which the catalyst is introduced. There are, for example, four radial orifices 68 spaced equally about the circumference of the reducing element 60. Thus, reducing element 60 in combination with the bore 38 provides an axial annulus of the primary fluid flowing through the radial circumferentially rotating sheet of catalyst.
The reducing element 60 does not extend totally through the first bore 38 and thus a portion 70 of the bore 38 has a substantially enlarged cross-sectional area compared to the annulus portion 64 produced by the reducing element 60. This enlarged chamber 70 is a dispersing chamber for further mixing the mixed catalyst and primary fluid by turbulence produced by the change of the cross-sectional area from the annulus section 64 to the section 70 of bore 38. The chamber 70 leads to the nozzle 22 through the primary fluid nozzle portion 24 mounted therein.
The cross-sectional area of the annulus portion 64 which produces the axial flowing primary fluid annulus and the width of the circumferential orifice 56 through which the catalyst is introduced radially are chosen so as to produce a high flow velocity of the primary fluid. This high flow velocity will generate a pressure gradient at the circumferential orifice 56 which will draw the catalyst into the primary fluid flow. As the spray orifice is increased in size, volumetric flow through annular passage 64 is greater and thereby creates an increased flow of velocity past the circumferential orifice 56. Thus, under these conditions, the injection pressure of the catalyst is maintained at approximately 50-75% of the injection pressure of the primary fluid.
It has been found that if the cross-sectional area of the annulus 64 is not maintained sufficiently small, the radially penetrating catalyst will not penetrate and thoroughly mix with the primary fluid flow. Similarly, since the fluids being introduced are orthogonal to each other, they are not operating against each other building up back pressure and therefore requiring greater injection pressures. Additionally, the use of the dispersing chamber 70 further increases the mixing of the resin and the catalyst.
The relationship between the size of the circumferential orifice 56 and the annular primary fluid flow passage 64 and the primary fluid flow rate produces the pressure gradient that provides the self-balancing system. With increase or decrease of volumetric flow, the inlet pressures will also appropriately change, thus keeping a constant ratio of the inlet pressures irrespective of flow rate changes. The circumferential orifice 56, has a cross-sectional width in the range of 0.004 to 0.007 inches. The annular passage 53 has a radial width in the range of 0.008 to 0.010 inches. The radial width of the annular passages 52 and 48 are in the range of 0.070 to 0.075 inches. The axial annulus 64 has a radial width of 0.02 to 0.03 inches. The bore 38 has a diameter in the range of 0.502 to 0.504 inches.
To prevent surges and act as an accumulator, restrictor 80 is provided in the line connected between inlet port 16 for the catalyst and the second axial bore 40. Restrictor 80 provides an annular restriction 82. The radial width of annulus 82 is between 0.004 and 0.005 inches. The overall length of the restrictor 80 is in the range of 1 to 1.5 inches. It should be noted that the restrictor 80 is short compared to the 25 foot restrictor of prior art internal mixing devices. The use of an annular restrictor provides a higher cross-sectional area than would a smaller diametric orifice with equivalent restricting characteristics.
The internal mixing cartridge 30 may be used with any make or model of spray gun and with any nozzle structure. The position of the axial bore 40 for the secondary fluid and the position or even existence of the axial bore 41 for air will be different to match those for each make and model. The nut 28 would be longer than the standard nut to mount the mixing cartridge 30 and the nozzle structure 22 to the housing 10. Thus, an external mixing spray gun can be easily converted into an internal mixing spray gun.
Although the examples contained herein have used resin and catalyst mixtures, the system can also be used preferably for any two component systems for mixing a small amount of a secondary fluid into a primary fluid. The system operates successfully in mixing low viscosity secondary fluids in high viscosity primary fluids.
Thus it can be seen that an improved internal mixing gun has been provided.
Although the present invention has been described and illustrated in detail, it is to be clearly understood that the same is by way of illustration and example only, and is not to be taken by way of limitation. The spirit and scope of the present invention are to be limited only by the terms of the appended claims.
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US2072281 *||Sep 23, 1936||Mar 2, 1937||Des Procedes Simonin Soc Et||Mixing and atomizing apparatus for hydrocarbons and other fluid materials|
|US2149115 *||Nov 27, 1936||Feb 28, 1939||Socony Vacuum Oil Co Inc||Oil burner|
|US3286997 *||Apr 18, 1961||Nov 22, 1966||Thiokol Chemical Corp||Vortex fuel injector|
|US3709468 *||Feb 10, 1971||Jan 9, 1973||Ives F||Static mixing dispenser and mixing method|
|US3727844 *||Apr 30, 1971||Apr 17, 1973||Eaton Corp||Dispensing apparatus|
|US3763876 *||Mar 21, 1972||Oct 9, 1973||Ransburg Electro Coating Corp||Fluid valve and mixing assembly|
|US3770208 *||Nov 23, 1970||Nov 6, 1973||Ethyl Corp||Mixing nozzle|
|US3790030 *||Nov 8, 1971||Feb 5, 1974||Ives F||Liquid resin spray dispensers|
|US4340311 *||Sep 26, 1980||Jul 20, 1982||Zebron Corporation||Interfacial surface generator mixer|
|U.S. Classification||239/400, 239/405, 366/165.1, 239/432, 239/427.5|
|International Classification||B29B7/74, B05B7/08, B05B7/10|
|Cooperative Classification||B05B7/10, B29B7/7438, B05B7/08|
|European Classification||B29B7/74D, B05B7/08, B05B7/10|
|Apr 5, 1988||AS||Assignment|
Owner name: GRAVES SPRAY SUPPLY, INCORPORATED CLEARWATER, FLOR
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:SMITH, JAMES E.;REEL/FRAME:004880/0355
Effective date: 19880209
|Feb 9, 1993||REMI||Maintenance fee reminder mailed|
|Jul 11, 1993||LAPS||Lapse for failure to pay maintenance fees|
|Sep 28, 1993||FP||Expired due to failure to pay maintenance fee|
Effective date: 19930711